Vincent Fleury: Dynamic topology of the cephalochordate to amniote morphological transition: A self-organized system of Russian dolls

It takes a physicist, and not your random physicist but a very special one, Vincent Fleury, to teach you that the Cephalochordata have no head! How ignorant one must be to say that a subphylum named after the particularity that the notochord is reaching into the head, yes head|tête|κεφαλή, has no head?

This comes straight out of his new paper: V. Fleury, Dynamic topology of the cephalochordate to amniote morphological transition: A self-organized system of Russian dolls, C. R. Biologies (2011), doi:10.1016/j.crvi.2010.11.009 [Abstract & Résumé]

Fleury is observing the world through the keyhole of his theory, nicely summarized here, and that may explain how he came to see the anatomy of the chorion as a dorsal fold (which de considered only for the amniotic folds as if the rest of the membrane didn’t existed)

And part of the principal subject of the paper concerned by the aneural hearts, as stated in the end of the introduction:

The remainder of this report, therefore, is a presentation of certain fundamental data on transmembrane potentials of the systemic and portal hearts of hagfish.

Along with the portal heart are gone the cardinal hearts (not mentioned by Jensen) described in 1926 by Cole (mentioned by Johansen, 1965, doi: 0.1111/j.1749-6632.1965.tb49417.x. And Fleury seems to think that the caudal heart is the aneural one:

The model would predict that there should exist animals with a heart located symmetrically to the heart in the chest, therefore near the tail. By searching in the litterature, I was surprised to see that it is indeed the case, there exist primitive fish, hagfish, with an aneural heart[8]

This note presents a mechanistic explanation of the transition between the morphology of cephalochordates to that of amniotes. By a careful study of the morphogenetic movements which occur during the early stages of development of a typical amniote (a chicken embryo), we are able to show that the formation of a vertebrate body follows a sequence: first, formation of dorsal folds, then head and heart as dorsal and ventral folds, and finally another dorsal fold, which eventually builds up the chorion. This order has a physical origin linked to the velocity field of the tissue flow. These folds form at right angles to the flow direction, and the topology of the chordates flow is hyperbolic. This mechanism explains the differences between the successive bauplans, by the cumulate forward and backward movement of the flow. Eventually, the entire phenomenon can be described as a self-organized system of Russian dolls, by which the heart finds itself inside the embryo, and the embryo itself inside the chorion. In addition, the phenomenon has a mirror symmetry in the anterior and in the posterior part, thereby explaining naturally the existence of animals having a caudal heart.